American International Group reported second quarter profit that fell well short of expectations, sparking an after-hours sell off in its shares.

As of 4:21 p.m., AIG shares had fallen 6 percent and were on track for their worst day since February 2017.

The insurance giant reported adjusted earnings per share of $1.05 for the quarter compared to the $1.21 expected by analysts as polled by Thomson Reuters.

Excluding one-time items, such as a $200 million charge for cost cutting, profit of $961 million was down from the $1.4 billion reported in the same period last year.

CEO Brian Duperreault, on the job for about a year, has put a focus on underwriting and improving technology to boost results. "In the second quarter, we continued to take actions across General Insurance to establish a culture of underwriting excellence and added stellar talent," he said in a press release on Thursday. "Our efforts are taking hold and we remain committed to achieving an underwriting profit as we exit 2018."

Total General Insurance, the unit that insures business customers, had a 46 percent decline in adjusted pretax profit. That was offset by better results in life and retirement products, which posted a 3 percent decline in pretax profit. Investment income for the company also slipped 12 percent in the second quarter.